Presently-known diaphragm pumps that are mass-produced generally have a suction capacity of the order of a water column of 4 meters (m) (and up to a water column of 7 m in special designs). This capacity can be increased by careful manufacture beyond the standards of mass production, resulting in special devices that differ from conventional pumps, in particular in terms of price. Such “special” pumps are of conventional architecture, with a compensation valve for compensating leaks of hydraulic oil (transmission oil leaks between the diaphragm and a piston that is mechanically driven back and forth), a rated safety valve for allowing hydraulic oil to escape in the event of excess pressure, and a device for de-gassing and purging air in order to evacuate, usually continuously, the air or gas that is present in the circuit firstly when the pump is put into operation and that comes secondly from gas that is dissolved in the oil itself and that returns to the gaseous state as a result of variations in the pressure of the medium that contains the gas in solution. The increase in the suction capacity of such “special” pumps results from the care applied to the fabrication and to the assembly of each of the parts making up the moving equipment of the pump for the purpose of optimizing clearances and fitting between the various components.
There exists a need for pumps having high suction capacity (of the order of 9 m of water column) that are capable of being mass-produced, and thus with fabrication and assembly constraints that come within the ranges of tolerance that are normal for mass production in this field, in order to remain within market prices.